Yes, I checked to make sure the two plugs are seated snugly. There's a very small screw by the ear cushions that when removed shows the connections to the ear speaker and they seem okay. The speaker must have gone bad. It costs a minimum of $35 plus shipping to have them evaluated by Sennheiser. If not covered by warranty, and they're 4 years old so probably not covered, will cost more to repair than a new set; $50 with shipping & tax. Oh well, hello throw away society.
something else to packrat away so when the new one breaks in 4 years maybe I can cobble both together and make a good one.